unit 3: anatomy of herps

life history

series of changes undergone by an organism during its lifetime

larval amphibian life span

20 days to several years

hatching glands

helps dissolve gelatinous egg capsule in amphibians

reptile birthing types

viviparous, ovovivipary, ovipary, triggered by maternal hormones and requires penetration of amniotic membranes and eggshell

egg carcuncle (egg tooth)

keratinous protuberance that pierces membranes, only in tuatara, turtles and crocodilians

metamorphosis

transformation of larvae into a miniature adult, usually representing a shift in habitat, only (some) amphibians

during metamorphosis

altered gene expression, tissue restructuring, extensive cell death

heterochrony

alterations in the genetically-controlled timing of ontogenetic events that ultimately affects the body form of adults

paedomorphosis

developmental process in which a trait fails to develop to the point observed in the ancestral species, “gilled adult”

major tradeoff for eggshells

size limitations!

eggshell developmental challenges

temperature, moisture, gas exchange

temperature

tolerance lies within a range

moisture

surrounding water around immersed egg creates added barrier, which allowed inadequate gas exchange

gas exchange

burial of eggs can be a problem, influenced by soil permeability

Australian side-necked turtle

only known turtle to lay eggs underwater

growth

addition of new tissue in excess of that required for replacement

factors that influence growth

temperature, food quality and quantity

are ectotherms vulnerable to starvation?

NO! they just cease growth

determinate growth

growth usually stopping by sexual maturity

indeterminate growth

keep growing through life

sexual maturity

4 months to 40 years

longevity

3 years (small lizards) to 100 years (tortoises)

amphibian glands and skin structure

mucuous and granular (poison) glands, no epidermal scales, has keratin structures

mucous and granular (poison) glands

occur in all post-metamorphic amphibians and are widespread

parotid glands

common to toads

nuptial pads

seasonal, associated with breeding in frogs and salamanders

spadefoot toad

tools for digging

reptile skin

covered by scales/scutes, all limbed species have keratinous claws

osteroderms

body plates found under scales in the dermis of crocodilians, turtles and some lizards

Rathke’s (musk) glands

aggregation of glandular tissues that occur in most turtles, secretions may be odorous and used to deter predators

edcysis

sloughing or molting of skin cyclically or following a period of growth

amphibian ecdysis

days to weeks, involves stratum corneum, eat skin layers to “recycle”

stratum corneum

the outer layer of skin in amphibians

crocodilian and turtle ecdysis

epidermis grows continually, shed in pieces

lizard and tuatara ecdysis

shed in large pieces

snake ecdysis

shed in one big piece, leaves individuals vulnerable

chromatophores

pigment cells that affect color in amphibians

melanophores

black, brown or red

iridophores

reflect light

xanthophores

yellow, orange, or red

amphibian skull

reduced and portions remain cartilage throughout life

caecilian skulls

robust and thick for burrowing

ancestral squamate heads

rigid jaws, skull lifted as a unit

“hanging jaw” of squamates

allows for rotation of the lower jaw

teeth

most in reptiles are cone shapes and sit in a single, longitudinal row

solenoplyphous teeth

characteristic of vipers, hollowed out fangs that rotate out from the maxilla designed for venom delivery

turtle teeth

NO! keratinized beak

turtle esophagus

papillae-lined, keratinized projections

vomerine teeth

anterior and on the roof of mouth for gripping prey in amphibians

maxillary teeth

in the maxilla used for gripping prey in amphibians

urostyle

rod of fused postsacral (caudal) vertebrae in frogs instead of an elongated vertebral column, designed for impact and jumping

turtle vertebral column

fused to the shell (appear as ribs)

crocodilian vertebrae

regional differentiation, similar to humans

fracture planes

near the base of tail in the vertebrae, allow squamates to experience tail autotomy

limbs of amphibians

evolved for terrestrial locomotion

pectoral girdle

loses articulation with skull, allows for more independent movement between skull and limbs

pelvic girdle

becomes more elaborate and enlarged for living on land with limbs that support body

python and boa pelvic girdles

exist in vestiges

limb reduction

correlated with body elongation in squamates

caecilian limbs

lost all components of appendicular skeletons

frogs and salamander limbs

present and well-developed, 4 digits on forelimbs

partial eye

“third eye” in sphenodon, light receptive organ responsible for regulating circadian rhythms and thermoregulation

lateral line system

a series of pores on the head and body, and each pore contains a set of cilia that sense water pressure, light, and to locate food

pit organs

specialized structures in the dermis and epidermis that house infrared heat receptors in boas, pythons and vipers

inner ear

fluid-filled membranous sac containing sensory receptors and suspended in fluid-filled capsule

middle ear

contains the bones and muscular links, transfer vibration to the eardrum

outer ear

includes the tympanum

tympanum

the eardrum which is visible in many frogs and some turtles

herp eyes

laterally or dorsolaterally located

scleral ossicles

ring of bony plates that surround the cornea in reptiles

Jacobson’s vomeronasal organ

patch of sensory cells within the main nasal chamber that detects heavy moisture-borne odor particles

tongue extension

odor particles are captured from the air by the tongue in snakes

tongue retraction

odor particles mixed with fluid in the mouth are delivered to the ducts leading to the vomeronasal organs in snakes

amphibian respiration

lungs, highly vascular, thin-walled sacs

lepidosaur respiration

lungs, simple sac-like

snake lungs

single functional right and non-functional left

turtle respiration

lungs, rigid shell doesn’t allow for typical inhalation, so abdominal and pectoral girdle muscles expand body cavity

gills

structures in larvae and a few adult salamanders, 3 pairs on each side

spiracle

exit point for respiratory water in frog larvae

cutaneous respiraton

requires moist skin, drying prevents diffusion cross cell membranes, some groups are lungless (salamanders)

buccopharyngeal cavity

vascular tissue used by amphibians and turtles for respiration

cloacal breathing

AKA butt breathing, turtles